Yes, it has been improved continuously from use and experience. Since the white car build in the first half of this thread I have changed the front hoop of the roll cage slightly and added the extra triangulation to the bottom of the rear fork. Otherwise, the design is dimensionally the same.

The change to the roll cage was strictly for driver comfort; the white car's front roll cage hoop put pressure on my upper arms when cornering and became uncomfortable after a while. I simply raised and deepened the bends to get the vertical portion farther forward.

The extra braces were added to the bottom of the rear fork after I had a problem with frame flex! After I finished the white car and raced it twice I built the black car (which I still own). In my first practice session with the black car I kept hearing chain binding noise in every corner. About halfway through the 3rd lap the chain broke! The rear fork was twisting badly in every corner. The problem never occurred with the white car (different rear forks?), but since it showed up in the black car I have added the extra bracing to all subsequent chassis.